Stan Ștefan, Ramalho João P Prates, Holca Alexandru, Chiș Vasile
Faculty of Physics, Babes-Bolyai University, Str. M. Kogălniceanu 1, RO-400084 Cluj-Napoca, Romania.
Department of Chemistry and Biochemistry, School of Science and Technology, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal.
Molecules. 2025 Jul 18;30(14):3021. doi: 10.3390/molecules30143021.
1,3-Diphenylisobenzofuran (DPBF) is a widely used fluorescent probe for singlet oxygen (O) detection in photodynamic applications. In this work, we present an integrated experimental and computational analysis to describe its spectroscopic, photophysical, and reactive properties in ethanol, DMSO, and DMF. UV-Vis and fluorescence measurements across a wide concentration range show well-resolved S → S electronic transition of a π → π* nature with small red shifts in polar aprotic solvents. Fluorescence lifetimes increase slightly with solvent polarity, showing stabilization of the excited state. The 2D PES and Boltzmann populations analysis indicate two co-existing conformers (C and C), with C being slightly more stable at room temperature. TD-DFT calculations have been performed using several density functionals and the 6-311+G(2d,p) basis set to calculate absorption/emission wavelengths, oscillator strengths, transition dipole moments, and radiative lifetimes. Overall, cam-B3LYP and ωB97X-D provided the best agreement with experiments for the photophysical data across all solvents. The photophysical behavior of DPBF upon interaction with O can be explained by a small-barrier, two-step reaction pathway that goes through a zwitterionic intermediate, resulting in the formation of 2,5-endoperoxide. This work explains the photophysical properties and reactivity of DPBF, therefore providing a solid basis for future studies involving singlet oxygen.
1,3-二苯基异苯并呋喃（DPBF）是一种在光动力应用中广泛用于检测单线态氧（O）的荧光探针。在这项工作中，我们进行了综合的实验和计算分析，以描述其在乙醇、二甲基亚砜（DMSO）和二甲基甲酰胺（DMF）中的光谱、光物理和反应性质。在较宽浓度范围内进行的紫外-可见光谱和荧光测量显示，具有π→π*性质的S→S电子跃迁分辨率良好，在极性非质子溶剂中出现小的红移。荧光寿命随溶剂极性略有增加，表明激发态得到稳定。二维势能面（2D PES）和玻尔兹曼布居分析表明存在两种共存的构象异构体（C和C），在室温下C略更稳定。使用几种密度泛函和6-311+G(2d,p)基组进行了含时密度泛函理论（TD-DFT）计算，以计算吸收/发射波长、振子强度、跃迁偶极矩和辐射寿命。总体而言，对于所有溶剂中的光物理数据，cam-B3LYP和ωB97X-D与实验结果的吻合度最佳。DPBF与O相互作用时的光物理行为可以通过一个小势垒的两步反应途径来解释，该途径经过一个两性离子中间体，导致形成2,5-内过氧化物。这项工作解释了DPBF的光物理性质和反应活性，因此为未来涉及单线态氧的研究提供了坚实的基础。
